Ring-e substituted 4-cyano-3-secoyohimbanes and -cyano-3-secoalloyohimbanes

ABSTRACT

This disclosure describes compounds of the class of ring-E substituted 4-cyano-3-secoyohimbanes and 4-cyano-3secoalloyohimbanes useful as analgesics, anti-inflammatory agents, and central nervous system depressants.

ilnite States Patent Albriglit et al.

[ June 27, 1972 [54] RING-E SUBSTITUTED 4-CYANO-3- SECOYOHIMBANES AND-CYANO-3- SECOALLOYOHIMBANES [72] Inventors: jay Donald Albright; LeonGoldman, both of Nanuet, N.Y.

American Cyanamid Company, Stamford, Conn.

[22] Filed: Jan.1l,l971

[21] Appl.No.: 105,641

[73] Assignee:

Related US. Application Data [62] Division of Ser. No. 758,593, Sept. 9,1968, Pat. No.

[52] US. Cl. ..260/326.3, 260/287, 260/307 D, 260/3265 B, 424/2743,226,391 12/1965 Albright et al ..260/287 Primary Examiner-Alex MazelAssistant Examiner-Joseph A. Narcavage Attorney-Edward A. Conroy, Jr.

[ ABSTRACT This disclosure describes compounds of the class of ring-Esubstituted 4-cyano-3-secoyohimbanes and 4-cyano-3-secoalloyohimbanesuseful as analgesics, anti-inflammatory agents, and central nervoussystem depressants.

9 Claims, No Drawings RING-E SUBSTITUTED 4-CYANO-3-SECOYOHIMBANES AND-CYANO-3-SECOALLOYOI-II1VIBANES CROSS REFERENCE TO RELATED APPLICATIONThis application is a division of our copending application Ser. No.758,593, filed Sept. 9, l968, now US. Pat. No. 3,576,004.

BRIEF SUMMARY OF THE INVENTION rial wherein C==Z is selected fromthegroup consisting of C R is hydrogen or lower alkyl; R, is hydroxy,methoxy or methylthiomethoxy; R is hydrogen, hydroxy, methylt hiomethoxyor 3,4,S-trimethoxybenzoyloxy; R is hydrogen or methoxy; and R ishydrogen or carbomethoxy; with the proviso that when R is hydroxy ormethylthiomethoxy then R is hydrogen, and with the further proviso thatwhen R is hydrogen then R is hydrogen. Suitable lower alkyl groupscontemplated by the present invention are those having up to six carbonatoms such as, for example, methyl, ethyl, isopropyl, n-propyl,isobutyl, secQ-butyl, tert.- amyl, n-hexyl, etc. In accordancewithaccepted convention,

an a-substituent at the 3-, 15-, 16-, 17-, 18- and 20-positions isbehind the plane of the paper whereas a B-substituent at these positionsis in front of the plane of the paper. This is usually represented bya----bond for an a-substituent, a bond for a B-substituent, and a W bondwhere both are indicated.

DETAILED DESCRIPTION OF THE INVENTION The novel compounds of the presentinvention are, in general, white, tan or orange-brown crystalline solids(some being pale yellow non-crystalline glasses) having characteristicmelting points and absorption spectra. The compounds are soluble inorganic solvents such as lower alkanols, chloroform, acetone,N,N-dimethylformamide.

The novel compounds of the present invention may be readily prepared byreacting an appropriately ring-E substituted yohimbe alkaloid of thefollowing general formulas:

wherein R,, R R and R are as hereinabove defined, with cyanogen bromideunder solvolytic conditions. These starting materials for thepreparation of the novel compounds of the present invention arederivatives of yohimbane belonging to the normal, pseudo, allo andepiallo series depending upon the cis or trans fusion of the D and Erings and the configuration at the 3-positions. The preparation of theseappropriately ring-E substituted yohimbe alkaloid starting materials maybe found in the following references: Albright et al., J. Org. Chem. 28,38 (1963): Albright et al., J. Org. Chem. 30, 1107 (1965); and Albrightet al., J. Am. Chem. Soc. 89, 2416 1967).

The reaction is an important modification of the classical von Braunreaction which involves reaction of a tertiary amine with cyanogenbromide in an inert solvent such as chloroform, benzene, and the like.In general, the standard von Braun reaction gives derivatives containinga bromine atom or olefinic materials. In contrast, we have found that inan aqueous or lower alkanolic medium, ring opening of compounds ofstructures (IV), (V) and (VI) occurs between N(b) of the B- carbolineand C-3 to give 3-seco-4-cyano derivatives (1, II and III) with either ahydroxyl or a lower alkoxyl group at C-3, respectively. In the novelring opening reaction with cyanogen bromide, compounds with ana-hydrogen atom at C-3, whether of the normal or allo series, give3-seco cyanamide products which have a 62-substituent at C-3. However,compounds with a B-hydrogen atom at C-3, whether of the normal or alloseries, give mainly 3-seco products which have an asubstituent at C-3,along with some isomeric 3-seco derivatives with a B-substituent at C-3.

Preferably the ring opening reaction to produce 3-alkoxy-3-secocyanamide derivatives is carried out by reacting two moles of ayohimbane, pseudoyohimbane, alloyohimbane or epialloyohimbane derivativewith one mole of cyanogen bromide in a mixture of excess lower alkanOland a suitable organic solvent for l to 24 hours at to 25 C. In this wayone mole of a 3-seco derivative with a C-3 alkoxy group is obtainedalong with one mole of the hydrobromide salt of the starting alkaloid.Other solvents besides chloroform may be used. These include such inertdiluents as benzene, tetrahydrofuran, dichloromethane,N,N-dimethylformamide, dioxane and the like. If preferred, the reactingalcohol may be used alone as both the solvent and reactant. Reactantalcohol mixed with an inert solvent has been found advantageous becauseof the increased solubility of the reacting alkaloid derivatives-in amixed medium. Complete solubility in the reaction medium is notrequired, however, for reactions have been carried out in which the mainportion of the reacting alkaloid was not in solution at the start of thereaction.

An alternate procedure for the preparation of 3-seco derivatives with analkoxy group at C-3 is to react one mole .of a yohimbane,pseudoyohimbane, alloyohimbane or epialloyohimbane derivative with onemole of cyanogen bromide in the presence of an excess of an appropriatealcohol and one mole of a base such as diisopropylethylamine. Thepresence of a hindered tertiary amine such as diisopropylethylamineprevents the tying up of one-half of the starting alkaloid as theunreactive hydrobromide salt and allows complete conversion to a 3-secoderivative.

Preferably, likewise, for the preparation of 3-hydroxy-3- secocyanimidederivatives two moles of a yohimbane, pseudoyohimbane, alloyohimbane orepialloyohimbane derivative is reacted with one mole of cyanogen bromidein a mixture of tetrahydrofuran and excess water for l to 24 hours at 0to 25 C. Other solvents besides tetrahydrofuran may be used. Theseinclude solvents miscible with water such as dioxane, N,N-

,dimethylformamide, etc. it has also been found that certain 3-hydroxy-3-seco derivatives can be converted into C-3 alkoxy derivatives.For example, methyl 4-cyano-3a,l8B-dihydroxyl 1,17a-dimethoxy-3-secoalloyohimbanel 6B-carboxylate, on refluxing inethanol, gives methyl 4-cyano-l 1,17a-dimethoxy- 3a-ethoxy-lSB-hydroxyalloy'ohimbanel GB-carboxylate. The reaction is believed to beacid catalyzed.

The preparation of the novel 3-oxo-3-secocyanimides of this invention iscarried out by reaction of 3-hydroxy 3-seco-4 -cyano yohimbanes oralloyohimbanes with lead tetraacetate in glacial acetic acid. Thereaction may be carried out with inert solvents, such as chloroform,dichloromethane and the like, as diluents. Other oxidizing agents suchas manganese dioxide may be used to convert the 3-hydroxy-3-seco-4-cyanoderivatives to 3-ox0-3-seco-4-cyano compounds.

The novel compounds of the present invention are valuable centralnervous system depressants of low toxicity and were shown to possess CNSdepressant activity as determined by animal experiments as follows. Thecompounds were administered intraperitoneally to groups of five mice ata dose level of 50 mg./kg. of body weight. Then, minute counts of motoractivity for each group of mice are made by means of an actophotometerwhich is a photoelectric device consisting essentiallyof a circular cageholding six lightsdirected respectively at six. photoelectric cellsspaced evenly around the perimeter of the cage. A single count isrecorded automatically each time a mouse breaks a light beam, and thetotal of such counts during a given interval is a measurement of thetotal motor activity of the mice in the actophotometer. Counts of 250 orless are considered to indicate a significant reduction (more than twostandard deviations) of motor activity. Those compounds that appeared toreduce motor activity by 50 percent or more were administered toadditional groups of five mice at graded doses and tested similarly. Themotor depressant dose (MDD which caused a 50 percent reduction in motoractivity was then estimated from the dose response curve. In arepresentative operation, and merely by way of illustration, two typicalcompounds of this invention were shown toreduce locomotor activity asset forth in Table l below:

TABLE I Compound MDD in mgJkg. of body weightsecoyohimbane-4-carbonitrile 29 methyl 4-cyano-3a, l 8fl-dihydroxy-l l l7a-dimethoxy-3- secoalloyohimbanel GB-carboxylate 35 The novel compoundsof the present invention are active analgesics when measured by thewrithing syndrome" test for analgesic activity as described by Siegmundet al., Proc. Soc. Exptl. Biol. Med., Vol. 95, p. 729 (1957), withmodifications. This method is based upon the reduction of the number ofwrithes following the intraperitoneal injection of l mg./kg. of

is considered active if it reduces the total number of writhes in twotest mice from a control value of approximately 30 per pair to a valueof 18 or less. ln-a representative operation, methyl 4-cyano-3a-ethoxyl7a-hydroxy-3-secoyohimbanel 6 a-carboxylate, 3B-ethoxy-3-secoyohimbano[17, l 8-c]isoxazole and methyl 4-cyano-l l,l7a-dimethoxy3,B-ethoxy-l8,8- hydroxy-3-secoalloyohimbane-l6B-carboxylate all showed analgesicactivity when tested by this procedure at an oral dose of 25 mg./kg. ofbody weight. If desired, the median effective dose (ED for anyparticular compound may be calculated from the results obtained byrepeating this test in multiple groups of two mice each at each ofseveral graded dose levels.

A supplementary procedure which generally indicates analgesic oranti-inflammatory activity is based on the reduction ofcarrageenin-produced edema in the rat paw. Weanling Sherman strain ratsranging in weight from 50-55 grams are used and fed standard laboratorydiet ad libitum. Test compounds are administered to the rats by gavage(250 milligrams per kilogram of body weight in a volume of 1.7milliliters of buffered aqueous starch) 1 hour prior to challenge withcarrageenin. The challenge agent, carrageenin, is bought from MarineColloids, 2 Edison Place, Springfield, New Jersey, and prepared as asterile 1 percent suspension in 0.9 percent aqueous sodium chloride. Avolume of 0.05 milliliter is injected using a 26-gauge needle into theplantar tissue of the right hind paw of treated and untreated rats.Measurements of the volumes of the carrageenin inflamed right(challenged) paw and left (unchallenged) paw are determined 4 hourssubsequent ,to the-carrageenin challenge. The method of determining pawvolumes is carried out essentially as described by C. A. Winter et al.,in Proc. Soc. Exptl. Biol. Med. 111: 544-547 1962) using mercuryimmersion. The differences in volume between the two paws of each rat isconsidered to be the volume of the carrageenin-induced edema. The meanedema volume of eight control rats divided by the mean edema volume oftwo treated rats is calculated as the CH efficacy ratio. A compound isconsidered active in this test of the mean C/T efficacy ratio of 2consecutive tests is equal to, or greater than 1.43. By way ofillustration, methyl 4-cyano-3B-ethoxy-17a-hydroxy-3-secoyohimbane-l6a-carboxylate when tested by thisprocedure was found active with efficacy ratios (C/T) of2.32 and 1.85.

Additionally, the novel compounds of the present invention are activeanti-inflammatory agents when tested against yeastinduced pyrexia inrats as follows. To groups of three Sherman strain rats, weighing 55figrams each, are administered subcutaneously in the napes of the necks,0.6 milliliters of a 40 percent suspension of dried yeast in distilledwater. Each test compound is then administered orally at a dosage of 250milligrams per kilogram in a 2 percent acacia vehicle at 17 hourspost-challenge. Control rats are treated in a similar manner but are notgiven the test compounds. At nineteen hours postchallcnge the rectaltemperature of each rat is recorded. The averaged numerical temperaturefor each group is then appropriately inserted into the relationship ofcontrol rats minus treated rats, abbreviated C-T. The test is designedin three sequential states, so that an acceptable compound requiresthree testing stages although one, two or three stages may be requiredfor rejection. Those test compounds are judged active in which the C-Tvalue is above 0.44 at stage one, and the averaged C-T value of bothruns is above 0.55 at stage two, and the averaged C-T value of threeruns is above 0.61 at stage three, and at which latter point thecompound is accepted as an active anti-pyretic agent. If at any stagethe average of the C-T values is below the above mentioned criticalvalues, the compound is rejected as being inactive. In a representativeoperation, and merely by way of illustration, methyl 4-cyano-3B-ethoxyl7a-hydroxy-3-secoyohimbanelGa-carboxylate was active when measured inthe above test.

The invention will be described in greater detail in conjunction withthe following specific examples.

EXAMPLE 1 Preparation of methyl 4-cyano-3B-ethoxy-l7-oxo-3-secoyohimbanel a-carboxylate To a suspension of 5.88 g. of yohimbinonein 150ml. of chloroform and 75 ml. of ethanol was added 0.80 g. ofcyanogen bromide and the mixture was stirred vigorously for l6 hours.The mixture was filtered, the precipitatewas washed with chloroform andthe combined filtrate and washings were concentrated under reducedpressure to a yellow glass. Trituration with ethyl acetate-ether (7:3)and filtration removed a small amount of precipitate. The filtrate, onconcentration, gave 3.1 g. of a yellow glass. Purification bychromatography gave methyl 4-cyano-3fi-ethoxyl 7-oxo-3-secoyohimbanel 6a-carboxylate as an off-white glass.

EXAMPLE 2 Preparation of methyl 4-cyano-3B-ethoxy-l7a-hydroxy-3-secoyohimbanel 6a-carboxylate To a chilled solution of 14.2 g. ofyohimbane in 100 ml. of ethanol and 100 ml. of chloroform was added asolution of 2.33 g. of cyanogen bromide in 35 ml. of ethanol. Themixture was allowed to warm to room temperature and was stirred forhours. The precipitate of yohimbane hydrobromide was filtered off andwashed with chloroform and the combined filtrate and wash wasconcentrated under reduced pressure to a yellow glass. This wastriturated with acetone and the suspension was filtered and the filtratewas concentrated under reduced pressure to a glass. The glass wastriturated with ethyl acetate and the suspension was filtered and thefiltrate was concentrated under reduced pressure to yield 8.0 g. ofmethyl 4-cyano- 3B-ethoxyl 7a-hydroxy-3-secoyohimbanel 6a-carboxylate asa yellow glass.

EXAMPLE 3 Preparation of methyl 4-cyano-3B-ethoxy-l7-oxo-3-secoyohimbanel 6a-carboxylate A solution of 1.0 g. of methyl4-cyano-3B-ethoxy-l7ahydroxy-3-secoyohimbane-l6a-carboxylate in 10 ml.of dimethyl sulfoxide and 5 ml. of acetic anhydride was allowed to standat room temperature for 18.5 hours. The solution was poured onto ice andthe mixture was brought to pH 6.5-7 with ammonium hydroxide. The mixturewas extracted with chloroform and the chloroform extract was dried overmagnesium sulfate. Concentration of the extract under reduced pressuregave a gum which was partitioned between ether and water. The etherlayer was washed with water, dried over magnesium sulfate andconcentrated under reduced pressure to give 0.83 g. of a yellow glass.Purification by chromatography over silica gel with dichloromethane aseluant gave methyl 4- cyano-3B-ethoxy-1 7-oxo-3-secoyohimbanel6a-carboxylate as an ofl white glass.

EXAMPLE 4 Preparation of methyl 4-cyano-3a-ethoxy-l7a-hydroxy-3-secoyohimbanel 6a-carboxylate To a suspension of 1.42 g. ofpseudoyohimbine in 5 ml. of ethanol and 10 ml. of chloroform was added0.212 g. of cyanogen bromide. The mixture was stirred vigorously for l8hours and filtered to remove the precipitate of pseudoyohimbinehydrobromide. The filtrate was concentrated under reduced pressure to aglass. This was taken up in methanol, filtered to remove a precipitate,and the filtrate was concentrated to residue. This was dissolved inacetone, filtered to remove a precipitate, and the filtrate wasconcentrated. Filtration gave 0.20 g. of methyl 4-cyano-3a-ethoxy-l7a-hydroxy-3 -secoyohimbane-l6a-carboxylate as white crystals, m.p.l74-l76 C. v

The reaction was repeated as above and the reaction mixture, afterremoval of pseudoyohimbine hydrobromide by filtration, was concentratedunder reduced pressure to yield a glass. This was crystallized fromacetone to yield 0.50 g. of product as white crystals, m.p. l70- 1 74 C.

EXAMPLE 5 Preparation of SB-ethoxy-l7-oxo-3-secoyohimbane-4-carbonitrileTo a chilled mixture of 11.76 g. of l7-yohimbanone in 200 ml. ofchloroform and ml. of ethanol was added a solution of 2.33 g. ofcyanogen bromide in 25 ml. of ethanol. The mixture was allowed to warmto room temperature and was stirred for 18.5 hours. The precipitate ofl7-yohimbanone hydrobromide was removed by filtration and washed withchloroform and the combined filtrate and wash was concentrated underreduced pressure to a yellow solid. Trituration of the solid withmethanol and filtration gave 7.0 g. of 3,8-ethoxy-l7-oxo-3-secoyohimbane-4-carbonitrile as light tan crystals, m.p. 263-266 C.(dec.). Recrystallization from ethanol gave 40 g. of product as lighttan crystals, m.p. 290-292 C. (dec.

EXAMPLE 6 Preparation of 3B-ethoxy-17-oxo-3-secoyohimbane-4-car- Ibonitrile To a solution of 1.18 g. of l7-yohimbanone in 25 ml. ofchloroform and 10 ml. of ethanol was added 0.645 g. ofdiisopropylethylamine. To the stirred solution wasadded 0.466 g. ofcyanogen bromide. The mixture was allowed to stand at room temperaturefor 17 hours, and was then concentrated under reduced pressure to neardryness. To the residue 50 ml. of water was added. The mixture wasfiltered to yield, after washing with water, 1.40 g. of tan crystals,m.p. 23524 0 C. Recrystallization from ethanol gave 1.05 g. of3B-ethoxyl7 oxo-3-secoyohimbane-4-carbonitrile as tan crystals, m.p.278-28l C. (dec.)

EXAMPLE 7 Preparation of3B-hydroxy-l7-oxo-3-secoyohimbane-4-carbonitrile To a chilled suspensionof 11.76 g. of 17-yohimbanone in 400 ml. of tetrahydrofuran and 100 ml.of water was added 2.12 g. of cyanogen bromide. The mixture was allowedto warm to room temperature and was stirred for 16 hours. The mixturewas filtered to remove the precipitate of l7-yohimbanone hydrobromideand the filtrate was concentrated under reduced pressure to a volume ofabout 50 ml. The mixture was diluted with water and the suspension wasfiltered to yield, after washing with water, 7.00 g. of tan crystals,m.p. 246-25 2 C. (dec.). This was taken up in 650 ml. of hotchloroformethanol 1:1), filtered hot, and the filtrate was chilled andfiltered to yield 3.50 g. of off-white crystals. Recrystallization froma mixture of dimethyl sulfoxide, acetone and water gave 2.13 g. of3,8-hydroxy-17-oxo-3-secoyohimbane-4-carbonitrile as off-white crystals,m.p. 27 l273 C. (dec.).

The reaction was repeated as above and the reaction mixture, afterremoval of the precipitate of l7-yohimbanone hydrobromide, wasconcentrated under reduced pressure to about 125 ml. The solution wasdiluted with 500 ml. of water and the crystals which formed were removedby filtration and washed with water. The yield of tan crystals of3B-hydroxy-l 7- oxo-3-secoyohimbane-4-carbonitrile was 6.37 g.

EXAMPLE 8 Preparation of 3,17-dioxo-3-secoyohimbane-4-carbonitrile To asuspension of 6.07 g. of 3B-hydroxy-l7-oxo-3-secoyohimbane-4-carbonitrile in 220 ml. of glacial acetic acid was added7.98 g. of lead tetraacetate. The mixture was stirred vigorously undernitrogen for 30 minutes, filtered and the filtrate was poured onto amixture of ice and water. Dilution with cold water to a volume of 2liters and filtering gave a solid. This was washed thoroughly with waterand dried at50 C. to give 3.60 g. offine tan crystals, m.p. 218-222 C.(dec.). Chilling the filtrate overnight gave an additional 0.80 g. ofproduct, m.p. l90l95 C. The two crops were combined and dissolved inacetone-chloroform, (1:1 The solution was treated with activated carbon,filtered and the filtrate was concentrated under reduced pressure untilsubstantial crystallization occurred. Chilling and filtering gave 2.50g. of. 3,17- dioxo-3-secoyohimbane-4-carbonitrile as tan crystals, m.p.224-226 C.

EXAMPLE 9 Preparation of methyl 4-cyano-3B, 1 7a-dihydroxy-3-secoyohimbanel 6a-carboxylate To a chilled solution of 14.18 g. ofyohimb ine in 250 ml. of tetrahydrofuran and 100 ml. of water was added2.12 g. of cyanogen bromide. The mixture was allowed to stand at roomtemperature for 20 hours and was then concentrated to I remove thetetrahydrofuran. The aqueous mixture was diluted with water andextracted with chloroform. The chloroform extract was dried overmagnesium sulfate and concentrated under reduced pressure to give 9.0 g.of a pale yellow glass. The glass (5.0 g.) was chromatographed over 200g. of aluminum oxide (activity 111). Elution with chloroform-methanol(99: I) gave, after evaporation, 2.3 g. of methyl 4-cyano-3B,l7a-dihydroxy-3-secoyohimbane-16a-carboxylate as a pale .yellow glass,m.p. changes to gum above a 140 C., gum liquifies at 2 l 0-225 C. I

In a similar run, there was obtained 8.0 g. of product as a pale yellowglass. Chromatography over 500 g. of aluminum oxide (activity 111) gave,on elution with chloroform-methanol (99:1 6.4 g. of methyl4-cyan0-3B,l7a-dihydroxy-3- secoyohimbane- 1 a-carboxylate as a yellowglass.

EXAMPLE 10 Preparation of methyl 4-cyano-3B,l7a-dihydroxy-3-secoyohimbane- 1 a-carboxylate and methyl 4-cyano-3B,17ozdihydroxy-3secoyohimbane- 1 a-carboxylate To a suspension of 1.42 g.of pseudoyohimbine'in 22 ml. of tetrahydrofuran, 5 ml. of water and 5ml. of acetone was added 0.212 g. of cyanogen bromide. The soliddissolved in 5-10 minutes and the solution was allowed to stand at roomtemperature for 20 hours. The solvent was removed under reduced pressureuntil a gum separated, water and chloroform were added and the crystalsof pseudoyohimbine hydrobromide were removed by filtration. Thechloroform layer of the filtrate was separated, dried over magnesiumsulfate and concentrated under reduced pressure to a tan glass. Theglass was chromatographed over 50 g. of neutral aluminum oxide (activityIII) in chloroform-methanol (99.752025). The center cut of the firstpeak gave 0.170 g. of white crystals which were recrystallized fromacetone to give 0.085 g. of methyl 4- cyano-3a, 17a-dihydroxy-3-secoyohimbane-16a-carboxylate as white crystals, m.p.changes to a viscous mass at 150-l 60 C. An additional 0.1 10 g. ofproduct as white crystals was obtained from the fractions preceeding thecenter cut. Further elution of the column gave 0.085 g. of methyl4-cyano-3B,17 a-dihydroxy-3-secoyohimbane-16a-carboxylate as a paleyellow glass.

EXAMPLE 1 1 Preparation of methyl 4-cyano-17a-hydroxy-3-oxo-3-secoyohimbane-16a-carboxylate To a suspension of 1.58 g. of methyl4-cyano-3B,l7adihydroxy-3-secoyohimbane-l6a-carboxylate in 5 ml. ofglacial acetic acid and 5 m1. of dichloromethane was added 1.77 g. oflead tetraacetate. The mixture was stirred vigorously for 20 minutes andthe solvent was removed under reduced pressure. The gummy residue wastriturated with water and filtered and the pale yellow precipitate waswashed thoroughly with water. Partition chromatography of the solid 1.1g.) over 600 g. of diatomaceous earth with heptane-ethylacetatemethanol-water (50:50:l5:6) as solvent [hold back volume (l-lBV)of 850 ml.] gave 0.227 g. .of impure product in HBV 2.0-2.5.Recrystallization from ethyl acetate gave 0.087 g. of methyl 4-cyanol7a-hydroxy-3-o-xo-3 -secoyohimbane- 1 6acarboxylate as white needles,m.p. 268-270 C.

EXAMPLE 1 2 Preparation of methyl 4-cyano-17a-hydroxy-3-oxo-3-secoyohimbane- 1 6a-carboxylate 1 To a mixture of 3.54 g. of leadtetraacetate in 10 ml. of glacial acetic acid and 10 m1. ofdichloromethane was added, in three portions, 3.16 g. of methyl4-cyano-3B,l7a-dihydroxy- 3-secoyohimbane-la-carboxylate. The mixturewas chilled briefly, allowed to stand for 15 minutes and the solvent wasremoved under reduced pressure. The gummy residue was triturated with200 ml. of cold water and filtered and the precipitate was washedthoroughly with water. Purification gave methyl4-cyano-17a-hydroxy-3-oxo-3-secoyohimbanela-carboxylate'as whiteneedles, m.p. 268-270 C.

EXAMPLE 13 Preparation of methyl 4-cyano-3B-ethoxy-l 7a-(methylthiomethoxy)-3-secoyohimban-l 6a-carboxylate To a solution of1.24 g. of methyl l7a-(methylthiomethoxy)yohimban-1a-carboxylate in 10ml. of ethanol and 10 ml. of chloroform was added 0.159 g. of cyanogenbromide. After 22 hours at room temperature the mixture was filtered andthe precipitate was washed with chloroform. The combined filtrate andwash was concentrated under reduced pressure to give a yellow solidwhich was triturated with methanol. The resulting yellow crystals werefiltered off and the filtrate was concentrated under reduced pressure toa glass. The glass was dissolved in chloroform and chromatographed oversilica gel. Elution with chloroform-methanol (99:1) (25 ml. cuts) gave,from cut six, 0.11 g. of methyl 4-cyano-3B-ethoxy-l 7a-(methylthiomethoxy)-3-secoyohimbane- 16a-carboxylate as a yellow glass,m.p. changes to a viscous mass at 1 10 C.

EXAMPLE 14 Preparation of 4-cyano-3B-ethoxy-3-secoyohimbano[ 17,18- c]isoxazole To a solution of 6.39 g. of yohimbano[ l7,l8-c]isoxazole in100 ml. of chloroform and 50 ml. of ethanol was added 2.84 g. ofdiisopropylethylamine and 2.12 g. of cyanogen bromide. The mixture wasallowed to stand at room temperature for 17 hours and was concentratedto near dryness under reduced pressure. The residue, containing gummymaterial, was diluted with water and the brown solid which separated wasremoved by filtration and washed with water. Air drying gave 8.00 g. ofproduct. Crystallization from ethyl acetate with the aid of activatedcarbon gave 1.80 g. of orange-brown crystals which were triturated withmethanol and filtered to give 1.30 g. of orange-brown crystals, m.p.205210 C. An additional 1.20 g. of crystals, m.p. l90-l95 C., wasobtained from the methanol filtrate. Recrystallization of the combinedcrops from ethanol gave 1.35 g. of 4-cyanO-3/3-ethoxy-3-secoyohimbano[17,18]isoxazo1e as orange-brown crystals, m.p. 208-211 C.

EXAMPLE 15 Preparation of methyl 4-cyano-3a-ethoxy-l8B-hydroxy-l1,17a-dimethoxy-3-secoalloyohimbane-16,8-carboxylate -3 ,4,5-trimethoxybenzoate To a solution of 12.16 g. of reserpine in 100 ml. ofchloroform and 100 ml. of ethanol was added 1.06 g. of cyanogen bromide.The solution was allowed to stand at room temperature for 17 hours andthe solvent was removed under reduced pressure to give a yellow solid.The solid was triturated with water, filtered, and washed thoroughlywith water. The dried solid was washed with portions of acetone (total160ml.) and the solution was concentrated to about 60 ml. Chilling andfiltering gave 2.64 g. of product as white crystals, m.p. sinters andslowly melts above 155 C. The original solid was extracted again withthree 100 ml. portions of acetone and the combined extracts wereconcentrated to a glass. Trituration with methanOl gave 1.20 g. ofproduct as pale yellow crystals, m.p. sinters and slowly melts above 150C. The combined crops of product were recrystallized from ethanol togive 3.16 g. of methyl 4-cyano-3a-ethoxy-l8B-hydroxy-l1,17a-dimethoxy-3-secoalloyohimbanel 6B-carboxylate 0-3 ,4,5-trimethoxybenzoate as white crystals, m.p., sinters and slowly meltsabove 155 C.

EXAMPLE 16 Preparation of methyl 4-cyano-l l,17o -dimethoxy-3a-ethoxy- 18fl-hydroxy-3-secoalloyohimbanel 6B-carboxylate To a chilled solution of12.43 g. of methyl reserpate in 100 ml. of ethanol and 100 ml. ofchloroform was added 1.59 g. of I cyanogen bromide. The mixture wasallowed to warm to room temperature and to stand for 17 hours. Thesolution was concentrated under reduced pressure to a glass. Triturationwith water, filtration, and washing with water gave crystals. Thecrystals were dissolved in chloroform and the solution was washed withwater, dried over magnesium sulfate and concentrated to a light tansolid. Trituration with methanol and filtration gave 5.10 g. of methyl4-cyano-l1,17a-dimethoxy-3aethoxy-l8B-hydroxy-3-secoalloyohimbane-16,3-carboxylateas white crystals, m.p. 258"260 C.

EXAMPLE l7 1 Preparation of methyl 4-cyano-l1,l7a-dimethoxy-3B-ethoxyEXAMPLE 18 Preparation of methyl 4-cyano-3a,l8B-dihydroxy-l1,170:-dimethoxy-3-secoa1loyohimbane- 1 6,8-carboxylate To a solution of 12.43g. of methyl reserpate in 200 ml. of tetrahydrofuran and 75 ml. of waterwas added 1.59 g. of cyanogen bromide. The mixture was allowed to standat room temperature for 18 hours. The solution was concentrated toremove the tetrahydrofuran and was diluted with water. The resultinggummy mixture was extracted with chlorofonn and with chloroform-ethanol(4:1). The extracts (without drying) were concentrated under reducedpressure, and the residue was dissolved in acetone. Removal of thesolvent under reduced pressure gave 11.8 g. of a yellow-orange glass.The glass was crystallized from chloroform to give 4.80 g. of product.Recrystallization from chloroform gave 3.70 g. of methyl 4-cyano-3a,18B-dihydroxy-1 1 ,1 7a-dimethoxy-3- secoalloyohimbane-l6B-carboxylate aspale yellow crystals, m.p. sinters to a glass above 155 C. and slowlymelts.

EXAMPLE 19 Preparation of methyl 4-cyano-11,17a-dimethoxy-3a-ethoxyl8,8-hydroxy-3-secoalloyohimbane- 1 6fi-carboxylate and methyl 4-cyano- 11 l 7a-dimethoxy-3BPethoxy- 1 8B-hydroxy- 3-secoalloyohimbane- 1fifi-carboxylate To a solution of 12.43 g. of methyl reserpate in 200m1. of tetrahydrofuran and 75 ml. of water was added 1.59 g. of cyanogenbromide. The solution was chilled briefly and allowed to stand at roomtemperature for 23 hours. The mixture was concentrated to near drynessunder reduced pressure. Ethanol was added and the solvent was removedunder reduced pressure. The residue was partitioned between water andchloroform-ethanol (9:1). The organic extract was dried over magnesiumsulfate and concentrated under reduced pressure to give 12.4 g. of aglass. The glass was dissolved in chloroform-acetone flzl) and filteredthrough a column of magnesium silicate. The column was washed with 2.5liters of chloroform-acetone (1:1) and with 1.5 liters ofchloroformmethanol (4:1 The combined washings were concentrated to give6.50 g. of glass. Chromatography over 200 g. of neutral aluminum oxide(activity 111) I gave, on elution with chloroform-methanol (99:1), 2.65g. of a 1:1 mixture of methyl 4-cyano-l l, l 7a-dimethoxy-3a-ethoxy-lBB-hydroxy- 3-secoyohimbane-l6fl-carboxylate and methyl 4-cyano- 1 1 17a-dimethoxy-3B-ethoxyl 8p!-hydroxy-3-secoalloyohimbane-16,6-carboxylateas a yellow glass. Crystallization from methanol gave 0.90 g. of whitecrystals, m.p. 235238 C. Recrystallization from methanol gave 0.31 g. ofmethyl 4- cyano-l l ,1 7a-dimethoxy-3fl-ethoxy- 18B-hydroxy-3-secoalloyohimbane-l6B-carboxylate as white crystals, m.p.27027 2 C.

In a similar run the product was extracted with chloroform containing0.75 percent ethanol. Concentration of the chloroform extracts gave ayellow glass. Chromatography of 6.88 g. of the glass over 200 g. ofneutral aluminum oxide (activity Ill) and elution (100 ml. cuts) withchloroform-ethanol (997510.75) gave, after crystallization frommethanol, 0.45 g. of methyl4cyano-11,l7a-dimethoxy-3B-ethoxy-1SIR-hydroxy-3-secoalloyohimbane-l6B-carboxylateas white needles, m.p. 272-275 C.

EXAMPLE 20 Preparation of methyl 4-cyano-1l,l7a-dimethoxy-3wethoxylSB-hydroxy-3-secoalloyohimbane- 1 6B-carboxylate A solution of 0. 100 g.of methyl 4-cyano-3a, l 8/3-dihydroxyl 1 17a-dimethoxy-3-secoalloyohimbane- 1 6B-carboxylate in 10 ml. of absoluteethanol was refluxed for 4 hours. The solvent was removed under reducedpressure and the residual glass was triturated with methanol to givecrystals. Filtration gave methyl 4-cyano-ll,l7a-dimethoxy-3a-ethoxy-18B-hydroxy-3-secoalloyohimbane-16B-carboxylate as off-white crystals, m.p.254258 C.

3 ,673 ,2 14 11 12 EXAMPLE 21 011 Preparation of methyl 4-cyano-l l, l7a-dimethoxy- 1 8B- hydroxy-3-oxo-3-secoalloyohimbane-16B-carboxylate IITo a solution of 0.914 g. of methyl 4-cyano-3a,18B- 5 dihydroxy-l l l7a-dimethoxy-3-secoalloyohimbanel 6B-carboxylate in 25 ml. of glacialacetic acid was added 0.887 g. of R4 is hydrogen and the hydrogen at thezo position has the lead tetraacetate..'l'he mixture was stirred for 25minutes and Confi uration was poured onto ice. The solution wasneutrallized with ION 3. compound according to claim 1 wherein C- =Z isC sodium hydroxide and extracted with chloroform. The ex- 10 0, R ishydrogen, and the hydrogen at the 20-position has the tracts were driedover magnesium sulfate and the solvent was B-configuration.

removed under reduced pressure to give a glass. The glass was 4. Acompound according to claim 1 wherein C 2 is dissolved in methanol andthe solution was concentrated to give crystals. Chilling and filteringgave 0.30 g. of pale yellow 00 m,

crystals, m.p. 275277 C. (dec. The crystals were dissolved inchloroform-methanol (3:2) and the solution was concentrated to 15 ml.Dilution with 5 ml. of methanol, chilling and filtering gave 0.23 g. ofmethyl 4-cyano-l1,17a-dimethoxyl EB-hydroxy-3-oxo-3-secoalloyohimbanel6B-carboxylate as off-white needles, m.p. 291- 292 c. (dec.). theB-configuratiom 5. A compound according to claim 1 wherein C-- Z isEXAMPLE 22 Preparation of methyl 4cyano-3B-ethoxy-l7a-hydroxy-3-secoalloyohimbanel 6/3-carboxylate (7 To a chilled mixture of 5.91 g. ofa-yohimbine in 50 ml. of 25 ethanol and 50 ml. of chloroform was added0.79 g. of cyanogen bromide. The solution was allowed to warm to room R1is hydrogen and the hydrogen at the zaposition has the temperature andwas stirred for 16 hours. The precipitate was fi configuration removedby filtration and washed with chloroform and the fil- 3O 6 A compoundaccording to claim 1 wherein C: Z is trate was concentrated in vacuo toa yellow glass. The glass was triturated with acetone and the acetonesolution was con- 0 02H! centrated under reduced pressure. The resultingglass was triturated with ether and filtered to give 3.00 g. of yellow 1crystals, m.p. l95-l98 C. Chromatography over silica gel It withchloroform-methanol (95:5) (200 ml. cuts) gave product 7 in fractionsthree and four. Crystallization from ether gave R is hydrogen, and thehydrogen at the 20-position has the 2.35 g. of methyl4-cyano-3B-ethoxy-l7a-hydroxy-3-SeCOalfl-configuration.loyohimbane-l6a-carboxylate as off white crystals, m.p. 7, A compound acordin to claim 1 wherein C=Z is 209-2l 1 C. 40 v We claim: 1 l. Acompound selected from the group consisting of those of the formula:

R is B-carbomethoxy, and the hydrogen at the 20-position has 3 N thea-configuration. C 8. A compound according to claim 1 wherein C=Z is RVQK 0H J Q R is ,B-carbomethoxy, and the hydrogen at the 20-position hasthe (rt-configuration.

9. A compound according to claim 1 wherein C Z is wherein C=Z isselected from the group consisting of OR H OC2H5 0:0, o and o C/ 0R HH... I H

R is selected from the group consisting of hydrogen and lower alkyl; andR is selected from the group consisting of hydrogen and carbomethoxy.

2. A compound according to claim 1 wherein C-" Z is R is B-carbomethoxy,and the hydrogen at the 20-position 5 has the a-configuration.

R is a-carbomethoxy, and the hydrogen at the 20-position has UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5: 73, DatedJune 27, 97

Inventor(s) Jay Donald Albright and Leon Goldman It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

I Column 1, line 55 "OR" should be OH i Column 2, line 7 "62" should beB Column 4, line 75 "of" should be if Column 7, line 70 "[5" should be aColumn 12, line 9 "C" should be C:

Signed and sealed this 23rd day of January 1973.

(SEAL) Attest:

EDWARD M. FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM PO-105O (10-69) USCOMM-DC 603764 69 i ".8. GOVIIIIIINTPRINTING 07PM! 1 III! O-QQl-Sl

2. A compound according to claim 1 wherein C Z is R4 is hydrogen, andthe hydrogen at the 20-position has the Beta -configuration.
 3. Acompound according to claim 1 wherein C Z is C=O, R4 is hydrogen, andthe hydrogen at the 20-position has the Beta -configuration.
 4. Acompound according to claim 1 wherein C Z is R4 is Alpha -carbomethoxy,and the hydrogen at the 20-position has the Beta -configuration.
 5. Acompound according to claim 1 wherein C Z is , R4 is hydrogen, and thehydrogen at the 20-position has the Beta -configuration.
 6. A compoundaccording to claim 1 wherein C Z is , R4 is hydrogen, and the hydrogenat the 20-position has the Beta -configuration.
 7. A compound accordingto claim 1 wherein C Z is R4 is Beta -carbomethoxy, and the hydrogen atthe 20-position has the Alpha -configuration.
 8. A compound according toclaim 1 wherein C Z is R4 is Beta -carbomethoxy, and the hydrogen at the20-position has the Alpha -configuration.
 9. A compound according toclaim 1 wherein C Z is , R4 is Beta -carbomethoxy, and the hydrogen atthe 20-position has the Alpha -configuration.